"Birds," Kim Masterson said. "Sound general quarters." As an alarm klaxon began blaring, she continued, "Helm, make our course two-six-zero by minus-one-six, distance two kilomters. Put the asteroid between us and them."

The klaxon ceased. "Aye, ma'am. How many are we expecting?" she asked.

"No idea," Kim said. "But it's probably the same number that hit the outpost the first time."

"Ma'am, we're in position behind the asteroid," said Petty Officer 2nd Class Amiyah Khan, who sat at helm.

"Acknowledged, Khan. Rig us for low emissions."

"Aye aye, rigging for low emissions," Khan said. The ship's lights dimmed, several uncrewed consoles on the bridge powered down, and Kim floated into her chair's harnesses as the ship's artificial gravity systems shut down. "We'll have about two hours before we have to vent the ship's heat sinks."

Objects with mass cannot travel faster than 300,000 kilometers per second, the speed of light in vacuum. Albert Einstein's special theory of relativity described this cosmic speed limit in the early 20th century. Physicists had hypothesized methods of bypassing the speed of light barrier as early as the late 20th century, but no one developed a working theory until Waqar al-Basri, a professor at the University of Baghdad, developed his theory of trans-dimensional travel in 2072. The Global Defense Force invested heavily in applying al-Basri's work, and after 16 years and more than $500 billion spent on research and development, they had developed the first operational trans-dimensional drive. The device shortened travel times between Earth and Mars from weeks or months to minutes and, later, made possible the first human visits to other stars.